Torchwood Four
From Tardis Wiki, the free Doctor Who reference
Torchwood 4 was a branch of the Torchwood Institute. The nature of this branch, its location, and its personnel where unknown. According to information passed from Torchwood 3 operative Jack Harkness to new recruit Gwen Cooper, Torchwood 4 he told her it was lost, though there was hope it would be found one day. (TW: Everything Changes)
